1. Field of the Invention
The invention relates to electrical stimulation of the body, and in particular a system, device and method for controlled and monitored electrical transcranial stimulation using cutaneous electrodes for medical treatment applications.
2. Description of the Prior Art
Transcranial Direct Current Stimulation (tDCS) is a method of applying low current electrical signals across the head in order to affect cognitive processes in a patient's brain as part of a medical treatment. Specifically, tDCS treatment is typically applied with currents in the 0 to 10 milliamperes (0 to 0.010 amperes) range. tDCS treatment has numerous medical applications that include treatment of drug addiction, post-stroke rehabilitation and treatment of depression.
tDCS treatment sessions are generally applied using a device containing a current source, such that a predictable amount of treatment current can be delivered to the patient, regardless of the impedance of the electrical pathway between a set of cutaneous electrodes. The device may be capable of generating differential output voltages of up to 80 volts or more.
In order to ensure the safety of the patient, it is necessary to ensure that the output current of the tDCS device does not exceed a safe level. If, due to a failure of electronics or programming, the output current were to exceed the prescribed safe level, serious injury to the patient could result, including damage to the patient's skin and brain.
In the past, fuses have been used as a safety means on electrical lines to provide overcurrent protection. However, due to the low currents used in tDCS treatments, fuses alone are not able to provide adequate protection to the patient, as there are no fuses on the market able to quickly interrupt a current of such small magnitude. Similarly, given that the range of safe tDCS currents may be narrow, fuses do not provide an adequately accurate threshold for protection. Fuses also cannot provide a nuanced approach to detecting abnormal conditions.
To ensure absolute safety of the patient receiving tDCS, there is a need for a reliable method of preventing the output current of the tDCS device from exceeding a pre-determined safe level, even in the presence of component failures, programming faults or abnormal circumstances. A system and method for preventing tDCS treatment current from exceeding a given level, even in the presence of multiple component failures is presented herein.